package cn.com.forever.LinkedList;

public class MergeTwoList {
    public static void main(String[] args) {

    }

    //递归解法
    public static ListNode mergetwolist(ListNode l1,ListNode l2){
        if(l1 == null){
            return l2;
        }
        if(l2 == null){
            return l1;
        }
        ListNode head = null;
        if(l1.val <= l2.val){
            head = l1;
            head.next = mergetwolist(l1.next,l2);
        }
        else{
            head = l2;
            head.next = mergetwolist(l1,l2.next);
        }
        return head;
    }
    //循环解法
    public static ListNode mergeTwolist(ListNode l1, ListNode l2){
        if(l1 == null){
            return l2;
        }
        if(l2 == null){
            return l1;
        }
        ListNode head = new ListNode(0);
        ListNode temp = head;
        while(l1 != null && l2 != null){
            if(l1.val <= l2.val){
                temp.next = l1;
                temp = temp.next;
                l1 = l1.next;
            }
            else{
                temp.next = l2;
                temp = temp.next;
                l2 = l2.next;
            }
        }
        if(l1 != null){
            temp.next = l1;
        }
        if(l2 != null){
            temp.next = l2;
        }
        return head.next;
    }
}
